Seed banks and seed dispersal: important topics in restoration ecology

Restoration ecology deals with the scientific and ecological background of nature management practices aiming at the re-establishment of plant species which have disappeared. As we focus on semi-natural landscapes, these disappearances can be caused by intensification of agricultural practices or cessation of human interference. Nature management practices attempt to re-establish the often species-rich original plant communities by the removal of nutrients (sod cutting, hay-making, grazing) after eutrophication (Schiefer 1984; Bobbink & Willems 1991; Oomes 1992; Bakker & OUT 1995), rewetting after severe drainage (Grootjans & Van Diggelen 1995; Koerselman & Verhoeven 1995), scrub and woodland removal (clear cutting, grazing) after bush encroachment (Willems 1988; Poschlod & Jordan 1992). The re-appearance of plant species may depend on their persistence in the soil seed bank as a ‘memory’ of the original plant community. If the species has been lost from the persistent soil seed bank, it has to be transported to the site of re-appearance by some vector, e.g. wind, water, animals, man, and incorporated into the fresh seed bank. The site of re-appearance after emerging either from the old seed bank or from the fresh seed bank has to be proven to be a safe site from the point of view of abiotic and biotic conditions (Harper 1977). Without the presence or arrival of seeds no re-appearance in the established vegetation will be possible. For this reason we focus on seed bank dynamics and seed dispersal in restoration ecology. We will present (i) a review of current methods of seed bank analysis including estimations of longevity and density, and (ii) the state of the art on methods and results of seed dispersal.